In case of suspicion of bacterial arthritis, the most important procedure:

• A. Initiation of antibiotic treatment
• B. Articular puncture and bacteriology
• C. X-ray exam
• D. Cooling the joint with ice

Answer: (B)

In suspected septic arthritis, the priority is to diagnose the infection quickly and tailor therapy to the organism. The best step is to perform an arthrocentesis to obtain synovial fluid for Gram stain, culture, and analysis. This direct sampling confirms whether bacteria are present, identifies the organism, and guides targeted antibiotic treatment, which is crucial to prevent joint damage. Draining the joint also provides immediate pain relief and reduces intraarticular pressure.

Imaging helps assess structure but isn’t diagnostic for infection in the acute setting, and cooling the joint doesn't address the infection. Starting antibiotics is important when septic arthritis is suspected, but obtaining synovial fluid for culture before or at the time of initiating therapy is essential to optimize pathogen-directed treatment and avoid obscuring the culture results.